Question

Julie sees commercials for antibacterial products that claim to kill almost all the bacteria in the area that has

been treated with the product. Julie asks, “How effective is antibacterial cleaner in preventing the growth of
bacteria?” She sets up an experiment in order to study the effectiveness of antibacterial products. Julie
hypothesizes that the antibacterial soap will prevent bacterial growth. In her experiment, she follows the
following procedure.
a. Obtain two Petri dishes with nutrient agar.
b. Rub a cotton swab along the surface of a desk at school. Then, carefully rub the nutrient agar with the
cotton swab without breaking the gel.
c. Repeat the same process with the other Petri dish.
d. Spray one of the Petri dishes with an antibacterial kitchen spray.
e. Carefully tape shut both of the Petri dishes and place them in an incubator.
f. Check the Petri dishes and record the results once a day for one week.
Identify the experimental variable and three control variables in the experiment.

Answer 1

Experimental variable: The antibacterial kitchen spray.

Control variables/ Constants: Same nutrient agar, Both placed in an incubator, Same location for collecting bacterial samples (desk at school).

Step-by-step explanation:

This experiment involves the study of the effectiveness of antibacterial products against bacterial growth. The independent variable is also called the experimental variable. It is the variable that the experimenter manipulates or changes in order to bring about an effect or response.

In this experiment, the independent/experimental variable is THE ANTIBACTERIAL KITCHEN SPRAY THAT WAS USED ON ONE OF THE PETRIDISHES. It is what the experimenter has control over in an experiment in order to effect a measurable response in the dependent variable, which is the GROWTH OF BACTERIA in this case.

Control variables of an experiment, also called Constants are the variables that an experimenter keeps unchanged for both the control and experimental group. They are kept constant in order not to affect the outcome of the experiment. The control variables in this experiment include: Same nutrient agar, placement in an incubator, Same location for collecting bacterial samples (desk at school).